1. Field of the Invention
This invention relates generally to integrated circuits which measure ambient temperature. Specifically, the present invention is a precision temperature sensor that produces an approximately linear capacitor charging current, which in turn is used to produce a clock frequency that is predictable with variances in ambient temperature. The invention incorporates a relaxation oscillator, two independent current generators, a reference oscillator and a frequency counter to compute ambient temperature. The invention is implemented on a single, monolithic integrated circuit.
2. Description of the Prior Art
The prior art is described by FIG. 1 which shows a typical integrated temperature sensor based on the well known .DELTA.V.sub.BE model that generates a voltage proportional to temperature. The prior art integrated circuit temperature sensors require a differential amplifier and an analog to digital (A-to-D) converter to convert a voltage from a diode, thermistor or other source into a digital temperature equivalent. The traditional, voltage oriented A-to-D converter may also require unnecessary hardware and software overhead not needed for temperature sensing applications. Furthermore, the prior art circuit requires a precision reference voltage which can be very costly depending on the requirements for accuracy.
Therefore, a need existed to provide a temperature sensor implemented on an integrated circuit which is capable of accurate measurement of temperature variations and which reduces complexity, board space and/or die area and pin count.